Axial flow compressors



Nov. 28, 1961 c. P. L. RlcKl-:T'rs

Axm. mow coMPREssoRs 2 Sheets-Sheet 1 Filed Dec. 10, 1956 Nov. 28, 1961 c. P. l.. RlcKETTs 3,010,643

AXIAL FLOW coMPREssoRs Filed Deo. 1o, 1956 2 sheets-sheet 2 portions of the bolts being reduced to a clearance diameter. For yadditionally locating the anges at the common interfaces a number of dowels 65 are inserted in circumferentially spaced holes 66 in the anges, the holes extending axially of the rotor.

The blades 10.carried by the discs 11, 12, 21, 22, 23, 24 and 25 are provided with lir tree roots 33 which lit into corresponding tir tree slots 34 in the rim of each disc in known manner. Suitably flanged rings such as 35 are disposed between the peripheries of adjacent bladecarrying discs in coaxial relation therewith to define the inner cylindrical surface of the working air passage between Ithe blades. between the discs and consequently air from the working air passage can creep into the annular chambers enclosed between these rings and the flanges 12a, 21a, 21b, 22a, 23a, 22b, 23b and 24a constituting the drum of the discand drum structure. The rings '35 are prevented from rotating relatively to the discs by dowels 67.

'Ihe shaft 60 has a frusto-conical end 36 provided with a flange 37 by which it is attached tothe rear end of the drum structure by the bolts 29 and the nuts 31.

Each of the blade-carrying discs is formed with a central bore 38 surrounded by a thickened hub portion. A tubular member 39 having an outwardly-directed ange 40 at its forward end and an inwardly-directed ange 41 lat its rearwardrend is interposed between the blade-carrying discs 12 and 21, the ange 40 being secured to the discs y11 and 12 and to the spigot 13 by the bolts 16 and the tlange 41 being secured to the disc 21 by nuts 43 and bolts 44 which pass through holes 45 in the ilange 41 and through aligning holes 46 in the thickened hub p0rtion of -the disc 21 at a lesser radius than the bolts 16.

The tubular member 39 strengthens the forward end of the rotor and forms part of means for resisting deection of the discs bounding separate chambers in the rotor under the action of unbalanced endwise pressure load on the discs as ywill hereinafter be fully described. The tubular member 39 also serves as part of a passage means or duct system for conveying air compressed in the compressor of which the rotor is lto form a part to a labyrinth seal (not shown) associated with the bearing 14, where the air is used for oil sealing and cooling purposes. The duct system further comprise a tubular member 47 itted in the bores 38 of the discs 21 and 22, a tubular member 68 fitted in the bores 38 of the discs 22 and 23 and three equally spaced tubes 52 extending radially from hollow bosses 50 provided on the ltubular member 68 through holes 54 in the flange 23a to ports 69 in the Vlring 35 constituting the inner boundary of the working air passage between the fourth and fifth rows of blades. The tubular member 68 is closed at Iits rearward end so Ithat air under pressure from between the fourth and fifth rows of blades is constrained to pass inwardly through the tubes 52 and ythen forwardly through the tubular members 68, 47 and 39 to the space within theV axial extensions 11b and 12b of the discs 11 and 12. From here the air passes outthrough openings 55 in the flange of the spigot 13- to the labryinth structure (not shown). Itwill be seen that this duct system dividesthe space within the drum structure into four separate chambers each of which is partly bounded by one or more of the discs and partly boundedby the anges constituting the drum structure. More specically, these chambers are firstly 70, bounded by the discs 12 and 21 and the anges 12a and 21a, secondly 71, bounded by the discs 21 and 22 and the anges 21b and 22a, thirdly 72, bounded by the discs 22 and 23- and the flanges 22b and 23a, and fourthly 73 bounded by the disc 23 and the anges 23b and 24a, This last chamber is in communication through the central openings 38 of the discs 24 and 25 with the hollow interior of the shaft 60.

YConsidering the chambers 70, 71 and 72, if these were completely airtight, the pressure Ain them would depend only on the running temperature, so that the direction and extent of the pressures acting axially upon the discs 'Ihese rings are not ytightly nipped` could be foreseen with reasonable accuracy. AIn practice however the facing joints between the parts are not completely airtight and the pressures in these chambers will ltherefore depend upon whether leakage occurs through the joints between the llange parts constituting the drum structure or through the joints between the discs and the tubular members forming the air duct. It is thus qui-te possible, for example, to have the pressure in the chamber 71 substantially equal to that between the third and fourth blade rows under one running condition and equal to that between the fourth and fifth blade rows under another running condition. Such a dilference would substantially alter the endwise loadings on the discs 21 and 22.

To avoid this indeterminate state of affairs passage means are provided from each of the chambers 70, 71, 72 and 73 through the drum structure constituted by the flanges 12a, 21a, 21b, 22a, 22b, 23a, 23b and 24a to the working air passage of the compressor. In the construction shown in the drawings these passages means take the form of shallow flat-bottomed slots 74 cut in the abutment faces of the flanges, at the interfaces 61, 62, 63 and 64, there being for example three such slots equally distributed around the abutment -face of each ange. The slots in the opposed faces are in alignment with one another as shown in HGURE 3 to form elongated holes. These slots also provide a convenient way of facilitating the separation of the discs during dismantling of -the rotor for overhaul by the driving in of wedge-shaped tools, the fact that the slots are opposite one another and flat bottomed enabling this to be done with minimum danger of damaging the abutment faces of the anges. To enable such tools to be inserted, holes 75 are provided inthe rings 35 opposite each of the slots 74. As already mentioned, the rings 35 are not normally so tightly fitting as to prevent all flow of air from the working air passage to the surface of the drum and thence through the slots 74, but nevertheless the holes 75 ensure that such cornmunication is maintained.

The existence of lthe slots 74 ensures that the pressures in the `chambers 70, 71, 72 and 73 will be graded in accordance with the stage by stage rise of pressure through the compressor and consequently the unbalanced endwise pressure loading on the discs 21, 22 and 23 is always towards the forward end of the rotor. The tubular members 47 and 68 are provided at each end with shoulders 49 which bear against the sides of the hub portions of the discs 21, 22 and 23 and consequently the unbalanced endwise pressure loads on lthe discs 22 and 23 are transmitted to the disc 21. The combined end- Wise load from all these discs is then transmitted through the tubular member 39, the hub portions of the discs 11 and 12 and the spigot 13 to the ball bearing 14 which acts as a combined journal and thrust bearing. Deflection of the discs 21, 22 and 23 under the action of unbalanced endwise pressure load is therefore resisted by the members 68, 47, 39, 11b, `12b and the spigot '13, which members act as a strut supporting the centres of the discs 21, 22 and 23 from the front compressor bearlng.

Slots similar to those shown at 74 may also be provided in the abutment faces of the `discs 24 and 25 and of a labyrinth seal member 76 to facilitate separation of these parts. Such slots admit to the chamber 73 supplies of air from between the sixth and seventh blade rows and from the outlet of the compressor but the pressure in the chamber 73 is not necessarily raised sincel air is drawn oi from this chamber from the rear end of the shaft 60 for cooling the turbine part of the rotor.

I claim:

A rotor drum for a multi-stage axial flow compressor comprising a plurality of axially spaced discs having opposed axial extending portions engaging each other, pairs of adjacent discs and axially opposed portions defining closed chambers, said portions defining the outer periphery of each of the closed chambers of a plurality of successive closed chambers, an annular ring of blades carried by each of the said discs on the periphery thereof, a venting passage from each of said chambers through said portions communicating each of said chambers with the flow stream `between the downstream and upstream faces of each pair of adjacent rings of blades, one of said blade-carrying discs being at the low pressure end of the rotor, the chamber between said low pressure blade-carrying disc and the next higher blade-carrying disc being the lowest pressure chamber and successive chambers toward the higher pressure end of the rotor being progressively higher pressure chambers, said blade-carrying discs having central apertures therein, tubular members dening the inner walls of said successive closed cham` bers and disposed along the axis of the rotor in the lowest pressure chamber and in the succession of higher pressure chambers, each tubular member having an axially directed abutment face at each end engaging corresponding abutment faces around said central apertures in the blade-carrying discs, the tubular members together forming a part of a continuous passage from the low pressure end of the rotor drum, the periphery of the drum at one of the high pressure stages having a conduit communicating the flow stream at that stage with the continuous passage.

References Cited in the tile of this patent UNITED STATES PATENTS 1,003,321 Belluzzo Sept. 12, 1911 1,008,531 Curtis Nov. 14, 1911 l2,528,635 Bell et al. Nov. 7, 1950 2,583,875 Ostman Ian. 29, 1952 2,610,786 Howard Sept. 16, 1952 2,639,885 Ledwith May 26, 1953 2,650,017 Pedersen et al Aug. 25, 1953 2,720,356 Erwin Oct. 11, 1955 2,742,224 Burhans Apr. 17, 1956 FOREIGN PATENTS 1,057,171 France Oct. 28, 1953 

